The school board in Compton, California, has voted to arm campus police officers with AR-15 rifles, according to the Los Angeles public radio station KPCC. Some parents and students are expressing discomfort, citing the same sorts of concerns sparked by the militarized police force of Ferguson, Missouri. In Compton, the local police union says its officers are hardly alone in seeking such weapons:

Currently, the following School Districts authorize their Police Officers to deploy these weapons; Los Angeles School PD, Baldwin Park School PD, Santa Ana School PD, Fontana School PD, San Bernandino School PD.

The police union goes on to defend the semi-automatic rifle for campus police officers:

If we encounter an active mass murderer on campus with a rifle or body armor, our officers may not adequately be prepared to stop that suspect. School Police Officers will undergo a training course, followed by a shooting proficiency test on a firing range and a written exam. The rifles are designed for increased accuracy and use rifled ammunition than can pierce body armor. The safety of our Students, Staff, and Parents are very important to us.

In a recent New York Times item, Ross Douthat rebutted just that sort of argument.

...the evidence that such sprees are sharply increasing is shaky and debatable, and the evidence that a more militarized police is necessarily crucial to stopping such killers seems thin as well. In Sandy Hook, for instance, the killer committed suicide about ninety seconds after the cops arrived; in Aurora, the killer surrendered to police; at Virginia Tech, the killer shot himself rather than engage with police. (At Columbine, things were more complicated: there were cops surrounding the school who didn’t fully engage until the SWAT teams arrived, which could be a case that the average cop should be trained more like a SWAT member … except that then the SWAT teams moved extremely slowly through the school as well, because even heavily armed and armored cops can be—understandably—loath to rush in without knowing how many active shooters they’re facing.)

From the D.C. sniper (picked up at a rest stop) to the Isla Vista killer (dead by suicide after a car chase), there just aren’t that many recent cases where a spree killer has gone down, Symbionese Liberation Army-style, after a long siege or in a hail of bullets that only a militarized police unit could deliver, or where specialized equipment has made all the difference to the cops. It’s much more common for such killers to either take their own lives or surrender, and when they’ve been stopped by return fire from cops, it’s usually been regular police units rather than SWAT teams that have done the necessary work.

None of this means, again, that SWAT teams shouldn’t exist; it should just cast doubt on the idea that every police department needs SWAT equipment and lots of it, and that arming them accordingly will make all the difference when a psychopath comes calling.

The campus officers in Compton are expected to be trained and have the new weapons within a month. And the nationwide trend of militarized police officers continues, even in schools with heavily armed city and county police agencies nearby. It's easy to imagine a lot of areas where extra training would benefit Compton's school resource officers—and hard to imagine AR-15 training is high on the list.

Conor Friedersdorf is a staff writer at The Atlantic, where he focuses on politics and national affairs. He lives in Venice, California, and is the founding editor of The Best of Journalism, a newsletter devoted to exceptional nonfiction.